The work proposed here is aimed at developing a clinically applicable system capable of making non-invasive, quantitative measurements from the in vivo human lens. The results will be analysed to identify changes in protein conformations in the lens accompanying cataractogenesis. Measurements of lens autofluorescence and lens light scattering will be used in combination to evaluate these changes. Lens autofluorescence measurements will provide information on those lens in which is incorporated a non-tryptophan fluoroprotein fluorescence. The light scattering measurements will be made using the techniques of photon correlation spectroscopy, which measures the temporal fluctuations in scattered light intensity caused by density fluctuations in the lens protein molecules. Analysis, in terms of theoretical models used to interpret the measured data, will provide information on the structural parameters of the lens proteins and their relative concentrations. The lenses of diabetics and non-diabetics will be evaluated with regard to protein changes occurring during aging and as a result of diabetes. The diabetic subjects will provide a short term model for the aging changes in the lens. The system will be used for monitoring longitudinal lens changes in order to evaluate the efficacy of anticataract treatments and for the prediction of early preclinical signs of cataract development.